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${ProjName}: |
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UART0_Terminal |
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Intended purpose: |
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To demonstrate the configuration and use of the USART module, in asynchronous |
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mode, while communicating with a terminal emulator. |
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Functional description: |
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* In this example UART0 communicates with a terminal emulator running on the PC, via a |
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USB-to-RS232 breakout cable or via the NXP LPC11Uxx VCOM serial port. |
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* The user is prompted to enter a string (not to exceed 32 characters), terminated by [Enter]. |
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* Each character that is entered is echoed back to the terminal by the UART0 |
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ISR, and the characters are stored in an array for future use. |
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* When the user types [Enter], a NUL character is appended to the array, and |
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a handshake flag is set by the ISR for the main routine. |
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* Upon seeing the handshake flag, the main routine prints the stored string to |
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the terminal, and the process repeats. |
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External connections: |
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* To use the NXP LPC11Uxx VCOM Serial Port: |
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1. No external connections are necessary. |
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2. The Max board must have the necessary solder-bump jumper modifications: |
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A. For LPC812 Max board, short pins 1 and 2 of both SJ1 and SJ4 |
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B. For LPC824 Max board, short pins 2 and 3 of SJ9 |
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C. For LPC845 Max board, no modification is needed. |
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C. For LPC802 LPCXpresso board, no modification is needed. |
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C. For LPC804 LPCXpresso board, no modification is needed. |
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3. The terminal emulator can then be connected to the NXP LPC11Uxx VCOM serial port which |
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enumerates when the board is connected. It appears something like this: |
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COM13: NXP LPC11Uxx VCOM serial port (COM13) |
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* To use a USB-to-RS232 breakout cable: |
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1. There are three external connections necessary: RXD and TXD based on the SWM |
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settings, plus a ground connection. The RXD and TXD pins can be chosen in chip_setup.h. |
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The defaults are as follows: |
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P0.25 = U0_TXD = breakout cable RXD |
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P0.24 = U0_RXD = breakout cable TXD |
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Board GND = breakout cable GND |
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Notes on the baud rate and FRG: |
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* The BRG and FRG settings are calculated in two steps, as follows: |
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// For asynchronous mode (UART mode) the formula is: |
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// (BRG + 1) * (1 + (m/256)) * (16 * baudrate Hz.) = FRG_in Hz. |
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// We proceed in 2 steps. |
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// Step 1: Let m = 0, and round (down) to the nearest integer value of BRG for the desired baudrate. |
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// Step 2: Plug in the BRG from step 1, and find the nearest integer value of m, (for the FRG fractional part). |
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// |
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// Step 1 (with m = 0) |
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// BRG = ((FRG_in Hz.) / (16 * baudrate Hz.)) - 1 |
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// = (30,000,000/(16 * 9600)) - 1 |
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// = 194.3 |
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// = 194 (rounded) |
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// |
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// Step 2. |
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// m = 256 * [-1 + {(FRG_in Hz.) / (16 * baudrate Hz.)(BRG + 1)}] |
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// = 256 * [-1 + {(30,000,000) / (16*9600)(195)}] |
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// = 0.002 |
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// = 0 (rounded) |
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Program Flow: |
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* This example runs with: |
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system_ahb_clk = 15 MHz. (main_clk = 15 MHz. FRO direct output) |
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UART0CLK = 15 MHz. (FRG0CLKSEL = main_clk, FCLKSEL0 = frg0clk) |
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See chip_setup.h and SystemInit() |
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* main() routine |
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1. Clocks to USART0 and the SWM are enabled. |
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2. The SWM is configured as per above. |
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3. The UARTCLKDIV and the FRG (both in SYSCON) are configured as per above |
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(for 9600 b.p.s.). |
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4. USART0 is given a peripheral reset. |
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5. USART0 BRG is configured as per above (for 9600 b.p.s.). |
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6. USART0 CFG register is configured for: |
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8 data bits |
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no parity |
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one stop bit |
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no flow control |
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asynchronous mode |
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no loop-back |
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7. USART0 CTL register is configured for: |
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no continuous break |
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no address detect |
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no Tx disable |
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no CC |
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no CLRCC |
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8. USART0 Rx Ready interrupt is enabled, and code execution enters the main while(1) |
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loop. |
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9. The user is prompted to enter a string, and each character is echoed by the |
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ISR back to the terminal until the NUL terminator is encountered. |
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10. When the NUL terminator is encountered, the ISR sets a handshake flag for |
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main, which prints the entire received string to the terminal, and the process repeats. |
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This example runs from Flash. |
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To run this code: |
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1. Build |
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2. Program memory, then reset target |
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or |
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2. Debug |
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3. Run or Go |
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Note: It may be necessary to power-cycle the board in order to regain control of the reset button after programming. |
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# Bibliothèque pour associer un écran e-paper à un LPC804 |
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